Note that this is all simulated, and it only covers that first half of the book. But a lot of people like it. It might help to figure out where to focus.

[In this project-centered course* you will build a modern computer system, from the ground up. We’ll divide this fascinating journey into six hands-on projects that will take you from constructing elementary logic gates all the way through creating a fully functioning general purpose computer. In the process, you will learn - in the most direct and constructive way - how computers work, and how they are designed.

What you’ll need:
This is a self-contained course: all the knowledge necessary to succeed in the course and build the computer system will be given as part of the learning experience. Therefore, we assume no previous computer science or engineering knowledge, and all learners are welcome aboard. You will need no physical materials, since you will build the computer on your own PC, using a software-based hardware simulator, just like real computers are designed by computer engineers in the field. The hardware simulator, as well as other software tools, will be supplied freely after you enroll in the course.

Course format:
The course consists of six modules, each comprising a series of video lectures, and a project. You will need about 2-3 hours to watch each module's lectures, and about 5-10 hours to complete each one of the six projects. The course can be completed in six weeks, but you are welcome to take it at your own pace. You can watch a TED talk about this course by Googling "nand2tetris TED talk".]

You'll see that quite a few people enjoy writing Forth for their computers. And then build applications on top of that. The PLC applications would be easy to write in Forth. You can find a lot of examples of really simple CPUs with Forth built on top of them. Just be careful not to get stuck on the Forth part - have some problem in mind that you want to solve.

Oberon is an example of a system that is simple enough for one person to understand.

The kit may still be available. It was fun to build and it has a simple version of Basic that was designed to take advantage of the Propeller capabilities. It connects to a PS-2 keyboard and a VGA monitor, and uses an SD card as a "hard drive".

Heater - I think that one could add that in without affecting the rest of the course. The way that they teach, it's just another layer of abstraction. In fact you could even build the gates out of legos or Minecraft redstone blocks ;-)

I can recommend the Nand to Tetris course if your goal is to learn the low level of how computers work. I didn't take the coursera version of the course, I just bought the Elements of Computing Systems book off Amazon and then followed the syllabus available here: http://www.nand2tetris.org/course.php.

The first half of the book, from what I remember, was devoted to creating the computer processor. This starts by using a simple nand gate and subsequently building the logic elements required to build a fully functional processor. The course provides software which you can use to test and simulate your logic elements at each level.

Whereas the first half of the book dealt with the hardware side of creating the processor through the use of writing HDL or Hardware Description Language, the second half of the book dealt with writing software that would run on that processor. You create a compiler which takes the high level language that the book uses, called Jack, and converts it into an intermediate language that then gets run through a virtual machine which turns the intermediate language into an assembly language called Hack. Then that gets run through an assembler you create which assembles the program down to the machine code which the processor can understand. The last few chapters of the book deal with writing an OS and actually creating a drawing program and games that run on the OS.

This course really provides a great overview of how computers are built from simple logic elements. It shows how complexity in these systems are managed by building simple modules which can be tested individually. Then these modules are connected together to build a finished system. This course also introduced me into the fascinating realm of FPGA's. The course doesn't go way in depth in any one area. But it gives you enough to at least possibly whet your appetite to research the areas that the book doesn't cover.

So, the thought is to take something like the BASIC Stamp or Propeller and create a computer comparable to the early 8088 based computers? With regards to microcontrollers, it would seem rare for these to be used to create such a computer, but like the early computers, you could put enough of them together to get the functionality you are looking for. Even the 8088 based systems had many peripheral devices that controlled I/O, keyboard input , video and such and the 8088 was just the main microprocessor that controlled it all. But, mind you, there is a difference between a microcontroller like the BASIC Stamp and a microprocessor like the 8088 so it is not a fair comparison between the two. But, as has been mentioned, the Propeller has some nifty features that allow it to behave similar to a basic computer system. The Hydra board was good for this and the Quick Start with a HIB add on board would get you close.

Do you have a degree in Computer Engineering or the equivalent? I would think most of your questions would have been answered there.

Propeller has some nifty features that allow it to behave similar to a basic computer system.

Quite so. More than one of us here has emulated the Zilog Z80 on the Propeller and created a late 70's vintage CP/M machine. Complete with SD card for the file system and VGA graphics for the console interface.

Even without emulating an older CPU and using an older OS a Propeller can be made in to an interactive machine in the style of those old 8 bitters.

Propeller has some nifty features that allow it to behave similar to a basic computer system.

Quite so. More than one of us here has emulated the Zilog Z80 on the Propeller and created a late 70's vintage CP/M machine. Complete with SD card for the file system and VGA graphics for the console interface.

Even without emulating an older CPU and using an older OS a Propeller can be made in to an interactive machine in the style of those old 8 bitters.

Propeller has some nifty features that allow it to behave similar to a basic computer system.

Quite so. More than one of us here has emulated the Zilog Z80 on the Propeller and created a late 70's vintage CP/M machine. Complete with SD card for the file system and VGA graphics for the console interface.

Even without emulating an older CPU and using an older OS a Propeller can be made in to an interactive machine in the style of those old 8 bitters.

I had seen the Propellerpowered Pocket Mini Computer sometime back and looks like a pretty cool project with the QuickStart board but I am not sure what the status of this is since most of the links are dead.

I had seen the Propellerpowered Pocket Mini Computer sometime back and looks like a pretty cool project with the QuickStart board but I am not sure what the status of this is since most of the links are dead.